Tag Archives: batch files

Replaceable parameters in batch file

This article is from our Febooti archive, it was relevant then, and I think that it is still relevant today (a few details changed).
Previous article: Stopping a DOS batch file.

console-wishmesh
Photo: freeimages.com

With the information covered so far we are able to use batch files to make our lives easier, and help our day to day computing operations. However, we could make our batch scripts more sophisticated by avoiding the big limitation that we have been faced with so far. That is – our files are hard-coded (written in stone, so to speak) and if we want to manipulate a file, we have to change the batch script again and again.

What if we wanted to perform a particular operation on a different file each time? We can use replaceable parameters to help us with this task. The two important factors in using replaceable parameters are – how to code them in the batch file, and second – how to give the values for the replaceable parameters to the batch file. The latter is rather quite easy. Replaceable parameters are to be entered after the batch file name and before pressing the Enter key. For example:

C:\>batch-params.bat Par1 Par2 Par3 Par4 Par5

Either a space or a comma character separates each parameter. Both are treated the same. Now, how many replaceable parameters does the above line have? The obvious answer would be five. This would be wrong. DOS counts the name of the batch file itself as a parameter, so there are 6 replaceable parameters on this line. Much like other programming languages DOS names them %0, %1, %2, %3, %4, %5 rather than %1 through %5.

DOS uses replaceable parameters as if they do not exist – for example, everywhere you see a replaceable parameter, the DOS sees the value of that parameter. When a batch script executes with ECHO ON, the DOS precedes each command in the batch file prompt. DOS treats the commands in the batch file exactly like it would if you entered them from the DOS prompt.

:: batch-params.bat
:: Example with Replaceable Parameters.
ECHO %1
ECHO %2
SHIFT
ECHO %2

The first 2 lines are remark statements that show the name of the file and a brief description of the program. The third line echo’s the first replaceable parameter entered on the command line. If replaceable parameter was not entered, the command will display the Echo is on message (just like with simple ECHO command). The fourth line shows the 2nd parameter. The fifth line shifts the argument. The line 6 acts like line 4, but because of SHIFT, it and echo’s third argument. SHIFT command allows to use more than 10 parameters / arguments in the batch file:

SHIFT changes the values of the batch parameters %0 through %9 by copying each parameter into the previous one. In other words, the value of %1 is copied to %0, the value of %2 is copied to %1, and so on. More in MS Help site.

The SHIFT command discards the first parameter %0, moves the remaining parameters down one value, and brings in a new value if one exists. Therefore after the SHIFT command gets read, the value in %1 is moved into %0, and the value in %2 moves into %1 and so on and so forth.

The SHIFT command really has two major purposes. First, by moving the parameters down into a lower replaceable parameter, a single replaceable parameter may be used for all coding by forcing the batch script to loop through the code. Second, it allows the batch file to handle more than nine replaceable parameters. The total number of replaceable parameters is constrained by the 127-character command line limitation (for old OSes), and starting Windows XP or later you can use longer command line – up to 8191 characters. A space, comma or semicolon is also a requirement to separate each replaceable parameter.

If you start our example batch file with the parameters: text1, text2, text3 and text4, you will see the following output:
C:\>batch-params.bat text1 text2 text3 text4
C:\>ECHO text1
text1
C:\>ECHO text2
text2
C:\>SHIFT
C:\>ECHO text3
text3
C:\>

And, note: we do not access fourth parameter (%4), so it is not shown in the console. Also, see the screenshot from Windows 8.1 CMD.exe:

Showing output example from the batch file with parameters
Showing output example from the batch file with parameters

Next article: Loops in the Batch files with examples.

This article is from our Febooti archive, it was relevant then, and I think that it is still relevant today (a few details changed).

Update Feb 21, 2015. Added link to the next article.

Stopping a DOS batch file

This article is from our Febooti archive, it was relevant then, and I think that it is still relevant today (a few details changed).
Previous article: First cmd / DOS batch script example.

Usually, OS (Windows, MS-DOS) executes a batch file without stopping. DOS stops processing the batch file while the program runs when the batch file loads a program. As soon as you exit the program, or an automatic termination occurs, OS immediately continues processing the batch file from where it left off. Typically this is what you want, but sometimes you want to give the user time to think, react, and then take action. An example would be giving the user a group of choices that you want them to select from before proceeding.

PAUSE is the command we are looking for. PAUSE stops the batch file until almost any key is pressed. A key that would produce a character on the screen needs to be pressed. Therefore pressing a key like CTRL or ALT or SHIFT will not exit out of the pause state. Earlier we used this command above to see the output on the console. Now we will use this to pause the execution of the batch script.

Though the PAUSE command is really quite helpful, it lacks in power. The keystroke that you press is not capable of being used as a menu selection nor can it be saved in the program in any other way. Below is an example to illustrate how the PAUSE command works along with the ways of terminating a program with the keyboard.

:: PAUSE-IT.bat
:: Example of the PAUSE command
:: and the ways to exit out of a program.
@ECHO OFF
ECHO The next command is a PAUSE
ECHO Do NOT press Ctrl+C or Ctrl+Break
PAUSE
ECHO Press Ctrl+C or Ctrl+Break on your keyboard
PAUSE

The first line is a comment with the name of the file. The second and third line comments are description of the program (batch file). The fourth line turns command-echoing off. Line 5 and 6 gives the first message about which keys you can press for the first example. Line 7 is the PAUSE command that stops the batch file until a key is pressed. The next line (8) displays the message about aborting the program using the keyboard controls. The last line (9) is the final PAUSE that finishes the program.

You can terminate this script in many ways, however, if you follow the ECHO instructions, then you will have the following output:

Batch file: press CTRL+Break CTRL+C
Batch file: press CTRL+Break CTRL+C

As you see in the screenshot, after pressing Ctrl+Break or Ctrl+C, the command interpreter asks you to “Terminate batch job (Y/N)?”. By pressing Y followed by the Enter, the batch file terminates.

Next article: Replaceable parameters in batch file.

UPDATE: Jan 15, 2015… added link to the next article.

This article is from our Febooti archive, it was relevant then, and I think that it is still relevant today (a few details changed).

What is a batch script?

This article is from our Febooti archive, it was relevant then, and I think that it is still relevant today (a few details changed).

Previous article: MS-DOS (cmd.exe) command prompt: CD, MD, copy.
Next article: First cmd / DOS batch script example.

Batch scripts is still relevant in 2014. Batch programming is repeatedly used in Windows server and workstation administration to make recurrent tasks easier and more efficient.

In the MS-DOS, Windows 95 and Windows 98, and nowadays in the DOSBox the most popular batch file is autoexec.bat. This file was appropriately named after AUTOmatic EXECution. Commands that are to be executed when DOS starts are placed in this special file particularly on systems that utilize the PROMPT and PATH commands. When pure DOS was the prevalent operating system this was important, however, on our newer Windows guided machines, this is really not of concern. The PATH environment variable can be modified from the System properties – Environment variables.

Environment variables - PATH - Windows 8.1
Environment variables – PATH – Windows 8.1

For creating and editing a batch file, I recommend to use Windows Notepad, or more advanced editor with syntax highlighting support, such as free and open source editor – Notepad++. You will save your batch files with a .bat or .cmd file extension. Some of the file naming conventions (requirements) for batch files include: not recommended to use any internal DOS commands for file names for example, ECHO.bat, ERASE.bat, PAUSE.bat, etc., and SPACES, and device names such as LPT, COM1, COM2, NUL, etc., and it is NOT OKAY to use the following special characters in a filename:

  1. \ – Backslash
  2. / – Slash
  3. : – Colon
  4. ? – Question mark
  5. * – Asterisk
  6. ” – Quotes
  7. < - Less than sign
  8. > – Greater than sign
  9. | – Pipe

The period must be used as the separator between the file name and the file extension. The colon is specifically used after a letter to identify a particular disk drive. The asterisk and question mark are special wild card characters. Be careful when using these two characters in your script as they can act on multiple files / folders, and with not planed carefully, do some very unpredictable things. The greater than sign, the less than sign and the pipe are special DOS commands to be discussed in the next articles. They are also illegal file names. When naming a DOS file you have even more restrictions.

It should also be noted that good recommended practice for batch file names is to not save them as the same name as another executable file with a different extension. If you already have a file named email.exe do not try to save the batch file as email.bat.

The format for batch files is a series of DOS commands on separate lines. Example:
First Command
Second Command
Third Command
Fourth Command
And so on...

Four types of commands are acceptable for a batch file. These are:

  1. internal commands
  2. .exe program names
  3. .com program names
  4. .bat / .cmd file names

As with any DOS procedure you can stop a batch program from executing by pressing CTRL+C or CTRL+Break key combination on the keyboard. DOS will ask if you wish to Terminate batch job (Y/N)?. Type N to skip the command you broke out of and proceed to the next command in the batch file. Press Y to abort execution of the batch file and return to the command prompt. Pressing ^Break will produce the same results as ^C (except some commands, like PING).

The last command that we will go over in this section is the VER command. VER stands for VERsion. Enter this into the command prompt and you will be presented with the current version of your DOS program / Operating System.
C:\>ver

The VER command displays the operating system version number
The VER command displays the operating system version number

This article is from our Febooti archive, it was relevant then, and I think that it is still relevant today (a few details changed).

Update Oct 6, 2014: added link to the next article.